The money and army bonuses seem to work properly but you only get 2x the items (for a power up that costs 5x more).

The effect of Free Cache has some luck factor.

Fizzer indicated the random factor was caped at 30%, which is beyond what I am seeing even if you assume +30% on the single use and -30% on the 10x use. Fizzer was not able to reproduce the error on his end so it may have something to do with the boosts, artifacts, research or level progression. I will be trying to reproduce the bug.

Another possibility is the difference of mining/smelting/crafting modifiers. The effect of Free Cache depends heavily on these modifiers. You can check the thread of Xeno and find how to abuse Market Raid. The same method should also apply to Free Cache.